Search

The interference between the $K^{+}{K}^{-}$ $S$-wave and $P$-wave amplitudes in $B_s^0\to J/\psi K^{+}{K}^{-}$ decays with the $K^{+}{K}^{-}$ pairs in the region around the $\varphi (1020)$ resonance is used to determine the variation of the difference of the strong phase between these amplitudes as a function of $K^{+}{K}^{-}$ invariant mass. Combined with the results from our $CP$ asymmetry measurement in $B_s^0\to J/\psi \varphi$ decays, we conclude that the $B_s^0$ mass eigenstate that is almost $CP=+1$ is lighter and decays faster than the mass eigenstate that is almost $CP=-1$. This determines the sign of the decay width difference $\Delta {\Gamma }_s\equiv {\Gamma }_L-{\Gamma }_H$ to be positive. Our result also resolves the ambiguity in the past measurements of the $CP$ violating phase ${\varphi }_s$ to be close to zero rather than $\pi$. These conclusions are in agreement with the standard model expectations.

We report the first observation of a baryonic $B_s^0$ decay, $B_s^0\to p\overline{\mathrm{\Lambda }}{K}^{-}$, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$. The branching fraction is measured to be $\mathcal{B}(B_s^0\to p\overline{\mathrm{\Lambda }}{K}^{-})+\mathcal{B}(B_s^0\to \overline{p}\mathrm{\Lambda }{K}^{+})=[5.46\pm 0.61\pm 0.57\pm 0.50(\mathcal{B})\pm 0.32(f_s/f_d)]\times {10}^{-6}$, where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the $B^0\to p\overline{\mathrm{\Lambda }}{\pi }^{-}$ decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of $b$-quark hadronization probabilities $f_s/f_d$.

The $B^{+}\to D^{+}{K}^{+}{\pi }^{-}$ decay is observed in a data sample corresponding to $3.0{\mathrm{fb}}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is $8\sigma$ and the branching fraction is measured to be $\mathcal{B}(B^{+}\to D^{+}{K}^{+}{\pi }^{-})=(5.31\pm 0.90\pm 0.48\pm 0.35)\times {10}^{-6}$, where the uncertainties are statistical, systematic and due to the normalization mode $B^{+}\to D^{-}{K}^{+}{\pi }^{+}$, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from $B^{+}\to D_2^{*}(2460{)}^0{K}^{+}$ and $B^{+}\to D^{+}{K}^{*}(892{)}^0$ decays. No significant signals are observed and upper limits are set on their branching fractions.

A search for the rare decay of a $B^0$ or $B_s^0$ meson into the final state $J/\psi \gamma$ is performed, using data collected by the LHCb experiment in $pp$ collisions at $\sqrt{s}=7$ and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. The observed number of signal candidates is consistent with a background-only hypothesis. Branching fraction values larger than $1.5\times 10^{-6}$ for the $B^0\to J/\psi \gamma$ decay mode are excluded at 90% confidence level. For the $B_s^0\to J/\psi \gamma$ decay mode, branching fraction values larger than $7.3\times 10^{-6}$ are excluded at 90% confidence level; this is the first branching fraction limit for this decay.

The associated production of a $W$ boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and $2.0{\mathrm{fb}}^{-1}$ collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The $W$ bosons are reconstructed using the $W\to \mu \nu$ decay and muons with a transverse momentum, $p_{\mathrm{T}}$, larger than 20 GeV in the pseudorapidity range $2.0<\eta <4.5$. The partons are reconstructed as jets with $p_{\mathrm{T}}>20\mathrm{GeV}$ and $2.2<\eta <4.2$. The sum of the muon and jet momenta must satisfy $p_{\mathrm{T}}>20\mathrm{GeV}$. The fraction of $W+\text{jet}$ events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the $W+b$ and $W+c$ production cross sections. The ratio of the $W+\text{jet}$ to $Z+\text{jet}$ production cross sections is also measured using the $Z\to \mu \mu$ decay. All results are in agreement with Standard Model predictions.

Using a $pp$ collision data sample corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay ${\mathrm{\Xi }}_b^{-}\to {\mathrm{\Lambda }}_b^0{\pi }^{-}$. No $b$ hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be $$\frac{f_{{\mathrm{\Xi }}_b^{-}}}{f_{{\mathrm{\Lambda }}_b^0}}\mathcal{B}({\mathrm{\Xi }}_b^{-}\to {\mathrm{\Lambda }}_b^0{\pi }^{-})=(5.7\pm 1.8_{-0.9}^{+0.8})\times {10}^{-4},$$where $f_{{\mathrm{\Xi }}_b^{-}}$ and $f_{{\mathrm{\Lambda }}_b^0}$ are the $b\to {\mathrm{\Xi }}_b^{-}$ and $b\to {\mathrm{\Lambda }}_b^0$ fragmentation fractions, and $\mathcal{B}({\mathrm{\Xi }}_b^{-}\to {\mathrm{\Lambda }}_b^0{\pi }^{-})$ is the branching fraction. Assuming $f_{{\mathrm{\Xi }}_b^{-}}/f_{{\mathrm{\Lambda }}_b^0}$ is bounded between 0.1 and 0.3, the branching fraction $\mathcal{B}({\mathrm{\Xi }}_b^{-}\to {\mathrm{\Lambda }}_b^0{\pi }^{-})$ would lie in the range from $(0.57\pm 0.21)\%$ to $(0.19\pm 0.07)\%$.

Decays of beauty baryons to the $D^{0}p{h}^{-}$ and ${\mathrm{\Lambda }}_c^{+}{h}^{-}$ final states (where $h$ indicates a pion or a kaon) are studied using a data sample of $pp$ collisions, corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected by the LHCb detector. The Cabibbo-suppressed decays ${\mathrm{\Lambda }}_b^0\to D^{0}p{K}^{-}$ and ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{K}^{-}$ are observed, and their branching fractions are measured with respect to the decays ${\mathrm{\Lambda }}_b^0\to D^{0}p{\pi }^{-}$ and ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{\pi }^{-}$. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon ${\mathrm{\Xi }}_b^0$ to the $D^{0}p{K}^{-}$ final state, and a measurement of the ${\mathrm{\Xi }}_b^0$ mass is performed. Evidence of the ${\mathrm{\Xi }}_b^0\to {\mathrm{\Lambda }}_c^{+}{K}^{-}$ decay is also reported.

First observations of the decays ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{D}_{(s)}^{-}$ are reported using data corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$ collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction $\mathcal{B}(B_s^0\to D^{+}{D}_s^{-})$ is made and a search is performed for the decays $B_{(s)}^0\to {\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{-}$. The results obtained are $$\begin{gathered} \mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{D}^{-})/\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{D}_s^{-})=0.042\pm 0.003(\text{stat)}\pm 0.003(\text{syst}), \\ \left[\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{D}_s^{-})}{\mathcal{B}({\overline{B}}^0\to D^{+}{D}_s^{-})}\right]/\left[\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{\pi }^{-})}{\mathcal{B}({\overline{B}}^0\to D^{+}{\pi }^{-})}\right]=0.96\pm 0.02(\text{stat)}\pm 0.06(\text{syst)}, \\ \mathcal{B}(B_s^0\to D^{+}{D}_s^{-})/\mathcal{B}({\overline{B}}^0\to D^{+}{D}_s^{-})=0.038\pm 0.004(\text{stat)}\pm 0.003(\text{syst)}, \\ \mathcal{B}({\overline{B}}^0\to {\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{-})/\mathcal{B}({\overline{B}}^0\to D^{+}{D}_s^{-})<0.0022[95\%\mathrm{C}\mathrm{.}\mathrm{L}\mathrm{.}], \\ \mathcal{B}(B_s^0\to {\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{-})/\mathcal{B}(B_s^0\to D^{+}{D}_s^{-})<0.30[95\%\mathrm{C}\mathrm{.}\mathrm{L}\mathrm{.}]. \end{gathered}$$Measurement of the mass of the ${\mathrm{\Lambda }}_b^0$ baryon relative to the ${\overline{B}}^0$ meson gives $M({\mathrm{\Lambda }}_b^0)-M({\overline{B}}^0)=339.72\pm 0.24(\text{stat})\pm 0.18(\text{syst)}\mathrm{MeV}/c^2$. This result provides the most precise measurement of the mass of the ${\mathrm{\Lambda }}_b^0$ baryon to date.

Violations of $CPT$ symmetry and Lorentz invariance are searched for by studying interference effects in $B^0$ mixing and in $B_s^0$ mixing. Samples of $B^0\to J/\psi K_S^0$ and $B_s^0\to J/\psi K^{+}{K}^{-}$ decays are recorded by the LHCb detector in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and $CPT$ symmetry. Results are expressed in terms of the standard model extension parameter $\mathrm{\Delta }{a}_{\mu }$ with precisions of $\mathcal{O}({10}^{-15})$ and $\mathcal{O}({10}^{-14})\mathrm{GeV}$ for the $B^0$ and $B_s^0$ systems, respectively. With no assumption on Lorentz (non)invariance, the $CPT$-violating parameter $z$ in the $B_s^0$ system is measured for the first time and found to be $\mathcal{R}e(z)=-0.022\pm 0.033\pm 0.005$ and $\mathcal{I}m(z)=0.004\pm 0.011\pm 0.002$, where the first uncertainties are statistical and the second systematic.

Decays of the ${\mathrm{\Xi }}_b^{-}$ and ${\mathrm{\Omega }}_b^{-}$ baryons to the charmless final states $p{h}^{-}{h}^{\prime -}$, where $h^{(\prime )}$ denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies $\sqrt{s}=7$ and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. The decay ${\mathrm{\Xi }}_b^{-}\to p{K}^{-}{K}^{-}$ is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the ${\mathrm{\Xi }}_b^{-}\to p{K}^{-}{\pi }^{-}$ decay. Results are reported, relative to the $B^{-}\to K^{+}{K}^{-}{K}^{-}$ normalization channel, for the products of branching fractions and $b$-hadron production fractions. The branching fractions of ${\mathrm{\Xi }}_b^{-}\to p{K}^{-}{\pi }^{-}$ and ${\mathrm{\Xi }}_b^{-}\to p{\pi }^{-}{\pi }^{-}$ relative to ${\mathrm{\Xi }}_b^{-}\to p{K}^{-}{K}^{-}$ decays are also measured.

A measurement of the $CP$ asymmetry in $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ decays is presented, based on $1.0{\mathrm{fb}}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011. The measurement is performed in six bins of invariant mass squared of the ${\mu }^{+}{\mu }^{-}$ pair, excluding the $J/\psi$ and $\psi (2S)$ resonance regions. Production and detection asymmetries are removed using the $B^0\to J/\psi K^{*0}$ decay as a control mode. The integrated $CP$ asymmetry is found to be $-0.072\pm 0.040(\mathrm{stat})\pm 0.005(\mathrm{syst})$, consistent with the standard model.

The time-dependent $CP$ asymmetry in $B_s^0\to J/\psi K^{+}{K}^{-}$ decays is measured using $pp$ collision data, corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96 000 $B_s^0\to J/\psi K^{+}{K}^{-}$ decays, the $CP$-violating phase ${\varphi }_s$ is measured, as well as the decay widths ${\mathrm{\Gamma }}_{\mathrm{L}}$ and ${\mathrm{\Gamma }}_{\mathrm{H}}$ of the light and heavy mass eigenstates of the $B_s^0–{\overline{B}}_s^0$ system. The values obtained are ${\varphi }_s=-0.058\pm 0.049\pm 0.006\mathrm{rad}$, ${\mathrm{\Gamma }}_s\equiv ({\mathrm{\Gamma }}_{\mathrm{L}}+{\mathrm{\Gamma }}_{\mathrm{H}})/2=0.6603\pm 0.0027\pm 0.0015{\mathrm{ps}}^{-1}$, and $\mathrm{\Delta }{\mathrm{\Gamma }}_s\equiv {\mathrm{\Gamma }}_{\mathrm{L}}-{\mathrm{\Gamma }}_{\mathrm{H}}=0.0805\pm 0.0091\pm 0.0032{\mathrm{ps}}^{-1}$, where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with $B_s^0\to J/\psi {\pi }^{+}{\pi }^{-}$ decays gives ${\varphi }_s=-0.010\pm 0.039\mathrm{rad}$. All measurements are in agreement with the standard model predictions. For the first time, the phase ${\varphi }_s$ is measured independently for each polarization state of the $K^{+}{K}^{-}$ system and shows no evidence for polarization dependence.

The first observation of the $B_s^0\to {\overline{D}}^{*0}\varphi$ decay is reported, with a significance of more than seven standard deviations, from an analysis of $pp$ collision data corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay $B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}$ and is found to be $\mathcal{B}(B_s^0\to {\overline{D}}^{*0}\varphi )=(3.7\pm 0.5\pm 0.3\pm 0.2)\times 10^{-5}$, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the $B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}$ decay. The fraction of longitudinal polarization in this decay is measured to be $f_{\mathrm{L}}=(73\pm 15\pm 4)\%$. The most precise determination of the branching fraction for the $B_s^0\to {\overline{D}}^0\varphi$ decay is also obtained, $\mathcal{B}(B_s^0\to {\overline{D}}^0\varphi )=(3.0\pm 0.3\pm 0.2\pm 0.2)\times 10^{-5}$. An upper limit, $\mathcal{B}(B^0\to {\overline{D}}^0\varphi )<2.0$ $(2.3)\times 10^{-6}$ at 90% (95%) confidence level is set. A constraint on the $\omega -\varphi$ mixing angle $\delta$ is set at $|\delta |<5.2°$ (5.5°) at 90% (95%) confidence level.

The first measurement of the production rate of ${\mathrm{\Xi }}_b^{-}$ baryons in $pp$ collisions relative to that of ${\mathrm{\Lambda }}_b^0$ baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and $1.6{\mathrm{fb}}^{-1}$ at $\sqrt{s}=7$, 8 and 13 TeV, respectively. In the kinematic region $2<\eta <6$ and $p_{\mathrm{T}}<20\mathrm{GeV}/c$, we measure $\frac{f_{{\mathrm{\Xi }}_b^{-}}}{f_{{\mathrm{\Lambda }}_b^0}}\frac{\mathcal{B}({\mathrm{\Xi }}_b^{-}\to J/\psi {\mathrm{\Xi }}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to J/\psi \mathrm{\Lambda })}=(10.8\pm 0.9\pm 0.8)\times {10}^{-2}$ [$\sqrt{s}=7,8\mathrm{TeV}$], $\frac{f_{{\mathrm{\Xi }}_b^{-}}}{f_{{\mathrm{\Lambda }}_b^0}}\frac{\mathcal{B}({\mathrm{\Xi }}_b^{-}\to J/\psi {\mathrm{\Xi }}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to J/\psi \mathrm{\Lambda })}=(13.1\pm 1.1\pm 1.0)\times {10}^{-2}$ [$\sqrt{s}=13\mathrm{TeV}$], where $f_{{\mathrm{\Xi }}_b^{-}}$ and $f_{{\mathrm{\Lambda }}_b^0}$ are the fragmentation fractions of $b$ quarks into ${\mathrm{\Xi }}_b^{-}$ and ${\mathrm{\Lambda }}_b^0$ baryons, respectively; $\mathcal{B}$ represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of $f_{{\mathrm{\Xi }}_b^{-}}/f_{{\mathrm{\Lambda }}_b^0}$ are obtained by invoking SU(3) symmetry in the ${\mathrm{\Xi }}_b^{-}\to J/\psi {\mathrm{\Xi }}^{-}$ and ${\mathrm{\Lambda }}_b^0\to J/\psi \mathrm{\Lambda }$ decays. Production asymmetries between ${\mathrm{\Xi }}_b^{-}$ and ${\overline{\mathrm{\Xi }}}_b^{+}$ baryons are also reported. The mass of the ${\mathrm{\Xi }}_b^{-}$ baryon is also measured relative to that of the ${\mathrm{\Lambda }}_b^0$ baryon, from which it is found that $m({\mathrm{\Xi }}_b^{-})=5796.70\pm 0.39\pm 0.15\pm 0.17\mathrm{MeV}/c^2$, where the last uncertainty is due to the precision on the known ${\mathrm{\Lambda }}_b^0$ mass. This result represents the most precise determination of the ${\mathrm{\Xi }}_b^{-}$ mass.

The production of charged hadrons within jets recoiling against a $Z$ boson is measured in proton-proton collision data at $\sqrt{s}=8\mathrm{TeV}$ recorded by the LHCb experiment. The charged-hadron structure of the jet is studied longitudinally and transverse to the jet axis for jets with transverse momentum $p_T>20\mathrm{GeV}$ and in the pseudorapidity range $2.5<\eta <4$. These are the first measurements of jet hadronization at these forward rapidities and also the first where the jet is produced in association with a $Z$ boson. In contrast to previous hadronization measurements at the Large Hadron Collider, which are dominated by gluon jets, these measurements probe predominantly light-quark jets which are found to be more longitudinally and transversely collimated with respect to the jet axis when compared to the previous gluon dominated measurements. Therefore, these results provide valuable information on differences between quarks and gluons regarding nonperturbative hadronization dynamics.

The Dalitz plot distribution of $B^0\to {\overline{D}}^0{K}^{+}{\pi }^{-}$ decays is studied using a data sample corresponding to $3.0{\mathrm{fb}}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. The data are described by an amplitude model that contains contributions from intermediate $K^{*}(892{)}^0$, $K^{*}(1410{)}^0$, $K_2^{*}(1430{)}^0$ and $D_2^{*}(2460{)}^{-}$ resonances. The model also contains components to describe broad structures, including the $K_0^{*}(1430{)}^0$ and $D_0^{*}(2400{)}^{-}$ resonances, in the $K\pi$ S-wave and the $D\pi$ S- and P-waves. The masses and widths of the $D_0^{*}(2400{)}^{-}$ and $D_2^{*}(2460{)}^{-}$ resonances are measured, as are the complex amplitudes and fit fractions for all components included in the amplitude model. The model obtained will be an integral part of a future determination of the angle $\gamma$ of the Cabibbo-Kobayashi-Maskawa quark mixing matrix using $B^0\to D{K}^{+}{\pi }^{-}$ decays.

A study of $B^{\pm }\to J/\psi {\pi }^{\pm }$ and $B^{\pm }\to \psi (2S){\pi }^{\pm }$ decays is performed with data corresponding to $0.37{\mathrm{fb}}^{-1}$ of proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$. Their branching fractions are found to be $\mathcal{B}(B^{\pm }\to J/\psi {\pi }^{\pm })=(3.88\pm 0.11\pm 0.15)\times {10}^{-5}\mathrm{\text{and}}\mathcal{B}(B^{\pm }\to \psi (2S){\pi }^{\pm })=(2.52\pm 0.26\pm 0.15)\times {10}^{-5},$where the first uncertainty is related to the statistical size of the sample and the second quantifies systematic effects. The measured $CP$ asymmetries in these modes are $A_{CP}^{J/\psi \pi }=0.005\pm 0.027\pm 0.011\mathrm{\text{and}}{A}_{CP}^{\psi (2S)\pi }=0.048\pm 0.090\pm 0.011$ with no evidence of direct $CP$ violation seen.

A search for $CP$ violation in $D^0\to K^{-}{K}^{+}$ and $D^0\to {\pi }^{-}{\pi }^{+}$ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$, collected using the LHCb detector at center-of-mass energies of 7 and 8 TeV. The flavor of the charm meson is inferred from the charge of the pion in $D^{*+}\to D^0{\pi }^{+}$ and $D^{*-}\to {\overline{D}}^0{\pi }^{-}$ decays. The difference between the $CP$ asymmetries in $D^0\to K^{-}{K}^{+}$ and $D^0\to {\pi }^{-}{\pi }^{+}$ decays, $\mathrm{\Delta }{A}_{CP}\equiv A_{CP}(K^{-}{K}^{+})-A_{CP}({\pi }^{-}{\pi }^{+})$, is measured to be $[-0.10\pm 0.08(\mathrm{stat})\pm 0.03(\mathrm{syst})]\%$. This is the most precise measurement of a time-integrated $CP$ asymmetry in the charm sector from a single experiment.

The doubly charmed baryon decay ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{+}{\pi }^{+}$ is observed for the first time, with a statistical significance of $5.9\sigma$, confirming a recent observation of the baryon in the ${\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ final state. The data sample used corresponds to an integrated luminosity of $1.7{\mathrm{fb}}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 13 TeV. The ${\mathrm{\Xi }}_{cc}^{++}$ mass is measured to be $3620.6\pm 1.5(\mathrm{stat})\pm 0.4(\mathrm{syst})\pm 0.3({\mathrm{\Xi }}_c^{+})\mathrm{MeV}/c^2$ and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be $[\mathcal{B}({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{+}{\pi }^{+})\times \mathcal{B}({\mathrm{\Xi }}_c^{+}\to p{K}^{-}{\pi }^{+})]/[\mathcal{B}({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+})\times \mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})]=0.035\pm 0.009(\mathrm{stat})\pm 0.003(\mathrm{syst})$.

A broad peaking structure is observed in the dimuon spectrum of $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be ${4191}_{-8}^{+9}\mathrm{MeV}/c^2$ and ${65}_{-16}^{+22}\mathrm{MeV}/c^2$, respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the $\psi (4160)$ meson. First observations of both the decay $B^{+}\to \psi (4160)K^{+}$ and the subsequent decay $\psi (4160)\to {\mu }^{+}{\mu }^{-}$ are reported. The resonant decay and the interference contribution make up 20% of the yield for dimuon masses above $3770\mathrm{MeV}/c^2$. This contribution is larger than theoretical estimates.